I bought a set of A* Z1-X or whatever gloves last year. The gloves are comfy, but the sizes run a bit small. I don't have big hands and the measurement chart on SafeRacer's website said I was right on the line between a Med & large. I bought Med hoping for a 'tight fit'. I couldn't even begin to fit my hand in there. returned them for a large, and it's still like stuffing sausages to get my hands in there. When my hands are cold and dry, they fit great. In the summer when I'm sweaty, they're a pain.
.... Because of all the tugging trying to get the undersized gloves on, I tore a small hole near a key seam about the 3rd or 4th time I wore them. I took a small piece of Nomex from an older pair of gloves and nomex thread and stitched it up. voila.
That said, The gloves are very comfy and breathe well so they stay relatively cool in the summer (once you can get them on!)
I wouldn't hesitate to buy them again, but I'd go another size larger.